Ultra high frequency device of the cavity resonator type



F. M. BAILEY June 3, 1947.

ULTRA HIGH FREQUENCY DEVICE OF THE CAVITY RESONATOR TYPE Filed May 13, 1943 Inventor:

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c W/ n B a H W H b Patented June 3, 1947 ULTRA HIGH FREQUENCY DEVICE OF THE CAVITY RESONATOR TYPE Francis M. Bailey, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application May 13, 1943, Serial No. 486,880

13 Claims. 1 My invention relates to ultra high frequency systems and more particularly to systems of the space resonant type.

It is an object of my invention to provide a new and improved ultra high frequency system. i

It is another object of my invention to provide a new and improved ultra high frequency amp1i-' fier of the space resonant type.

It is a further object of my invention to provide a new and improved ultra high frequency amplifier of the space resonant type which includes as a central or control element thereof an electric discharge device and means for defining a pair of space resonant cavities associated respectively with the anode-grid and the grid cath ode circuits of the discharge device.

It is a still further object of my invention to provide a new and improved method of operating an ultra high frequency space resonant system such as an amplifier.

Briefly stated, in accordance with one aspect of my invention, I provide a new and improved ultra high frequency system of the space resonant type which may be employed as an amplifier for lowwave length electromagnetic waves, and which is by virtue of the use of a minimum number of parts susceptible of easy fabrication and necessitates .a minimum number of adjustments in application or use. The system comprises means for defining a pair of space resonant regions or cavities which are respectively associated with the anode-grid and the grid-cathode circuits of an electric discharge device. The anode-grid cavity is preferably defined by an elongated cylinder of conductive character through Which ex tends a mechanism including a longitudinally positionable connecting rod and filtering or tuning means, adjustable with and preferably attached to the longitudinal rod, so that the tuning operation is readily accomplished by externally accessible meanslocate'd at one end of the cylinder. The other end of the cylinder extends to a point intermediate the grid and the cathode terminals of the discharge device and the part of this end of the cylinder constitutes means for defining one boundary of the grid-cathode cavity. The latter cavity is of substantially shorter longitudinal dimension and of larger diameter than the above mentioned cylinder, thereby reducing the size of the system. Tuning means are provided for the grid-cathode cavity and excitation means, such as input and output electrode means, are associated with the grid-cathode and the anode-grid cavities, respectively.

For a better understanding of my invention,

reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. Fig. 1 illustrates a cross sectional longitudinal view of one embodiment of my invention particularly adaptable for use as an ultra high frequency amplifier, and Fig. 2 represents certain operating characteristics thereof,

particularly the relationship between the gain and the operating wave length of the system.

Referring now more particularly to Fig. 1, my invention is there illustrated as applied to an ultra high frequency system of the space resonant type which may be employed as an ultra high frequency amplifier for operation within the micro-v wave region. As a central element or control device of the system, I employ an electric discharge device I which comprises a plurality of enclosed electrodes and which is preferably of the construction disclosed and broadly claimed in a copending patent application of James E; Beggs, Serial No. 436,633, filed March 28, 1942, and which is assigned to the assignee of the present application. The discharge device I comprises an anode 2, a grid 3 and a cathode 4 (preferably of the thermionic type), supported by transversely extending disk-like members 5, 6 and I, respectively, preferably having increasing diameters in the order named to facilitate connection to the structure which defines the space resonant cavities to be discussed presently.

Cathode 4 and the transverse member I are electrically insulated from each other, so far as unidirectional potentials are concerned, being in spaced relation or separated by an insulating material (not shown), thereby affording a high frequency connection by virtue of the capacitance effect therebetween.

The transverse members 5-7, inclusive, serve as externally accessible means or terminals, that is externally accessible with respect to the discharge device I. These transverse members are supported in the illustrated spaced relation by means of a pair of insulating cylinders, such as vitreous cylinders 8 and 9, sealed in end-to-end relation therebetween, and the above described structure may be supported by a base member 19 provided with a plurality of terminals or prongs I I, I2 and !3 and an orientation protuberance 14. Two of these prongs, such as prongs I! and I2, may be employed for supplying energizing current to a cathode heating element (not shown) and the remaining prong 13 may be employed for the impression of a unidirectional potential on the cathode structure.

The anode-grid cavity, that is the space resonant region associated with the anode-grid circuit of discharge device I, is defined by means of an elongated cylinder I5 of conductive character, preferably metallic, which is connected to transverse member 6 near one extremity or end. For example, the transverse member 6, which may be of disk form, is seated in an appropriately formed shoulder I6 provided on the inner surface of the cylinder I5, and the end II of cylinder I5 preferably extends axially or longitudinally to a position intermediate the transverse members 6 and I. The anode-grid cavity is defined, in part, by means of a longitudinal anode connecting rod I8 of conductive character which is provided with a recess I9 at one end thereof adapted to receive an anode adapter 20 electrically connected to anode 2 of discharge device I. Recess I9 is of sufficient size to permit axial and rotational movement of the rod I8, while at the same time maintaining electrical contact with the adapter 20. At the other end of the connecting rod I8 I provide a choke or filter member 2| preferably of cup-shape configuration and having an electrical wave length corresponding to one-quarter wave length of the operating frequency or range of operating frequencies of the system. The filter member is attached to and longitudinally positionable with the anode connecting rod I8. This mechanical connection may be obtained by any suitable mechanical expedient which may comprise a threaded bolt 22 which extends into the right-hand end of anode rod I8 and is anchored at the other end in a .conductive rod 23, thereby maintaining the closed end of member 2| fixed therebetween. The longitudinal or flanged part of member 2| is spaced from the inner surface of cylinder I5.

As a means for controlling the position of the anode rod I8 and the tuning member 2| in axial or longitudinal direction, I may employ a suitable mechanical means such as an end wall in the form of an insulating plug '24 inserted within the right-hand end of cylinder I5, and which is provided with a threaded aperture 25 adapted to engage threads 26 at one end of rod 23. At an externally accessible position I provide a positioning means, such as a knurled wheel 21, for rotation of rod 23 and which effects rotation and consequent longitudinal adjustment of anode connecting rod I8 and member 2|.

A suitable unidirectional potential may be supplied to the system by means of a spring biased contact 28 connected to rod 23 and consequently to the anode 2 through member 2| and rod I8.

Ultra high frequency energy may be derived from th anode-grid cavity by means of suitable output electrode means which may take the form of an electrostatic output means including a metallic disk 29 attached to oneend of the inner conductor of a concentric transmission line 30 comprising an inner conductor 3| and an outer tubular conductor 32 which may be maintained in desired spaced relationship by means of an annular vitreous insulator 33. The output electrode means is arranged to be positionable longitudinally or axially for controlling the amount of energy fed back to the grid-cathode cavity from the anode-grid cavity. This adjustable feature may be afforded by extending the upper end of inner conductor 3| through a longitudinal aperture 34 in cylinder I5, and by supporting the concentric transmission line 38, as well as the output electrode means, by an axially adjustable housing 35 which rests upon and is in slidable 4 engagement with the outer surface of cylinder I5. As a means for completing the definition of the grid-cathode space resonant cavity and for minimizing the size of the entire system, I provide an annular member 35 of conductive character surrounding device I. For example, the member 36 may be a metallic ring supported by a metallic collar 3! which is in turn supported by cylinder I5 and a flanged supporting ring 38 which engages discharge device I and is electrically connected to cathode transverse member I. The grid-cathode cavity is of larger diameter than the anodegrid cavity and is of substantially smaller longitudinal or axial dimension.

Electrode means, such as input electrode means, is associated with the grid-cathode cavity all) and may comprise an extension of an inner conductor 39 of a concentric transmission line comprising the inner conductor 38 and an outer tubular conductor 40. Inner conductor 39 at its lower extremity extends into the rid-cathode cavity nd is preferably connected to the cylinder I5 at or near the end thereof.

In order to tune the grid-cathode cavity, I provide means, such as a readily adjustable member II, which may be constructed either of a conductive material or a dielectric material. As an example, the tuning means may comprise a metallic screw extending through a threaded aperture 42 in a, part of ring 38. The position of the end surface 43 of member 4| may be considered as controlling principally the capacitance of the grid-cathode cavity and consequently controlling the natural frequency thereof.

The bias voltage effective on the grid 3 of the discharge device may be controlled in a variety of ways. One manner in which the bias voltage may be controlled is by the employment of an adjustable impedance or resistance 44 connected between the cathode prong I3 and the structure electrically connected to transverse member 6, such as ring 38, the entire metallic structure of the space resonant cavity, of course, being maintained at ground potential as illustrated.

Considering the natural frequency of the gridcathode cavity, this cavity is of fixed external dimension, the tuning effect being accomplished by member 4|. One manner in which the system may be operated is by the design and adjustment of the grid-cathode cavity so that its electrical length is an odd multiple of quarter wave lengths corresponding to the operating frequency, such as one-quarter wave length. The adjustment of member GI may 'be considered as adding or subtracting capacitance to or from grid 3 of discharge device I. The anode-grid cavity is preferably operated to have an electrical length corresponding to an odd multiple of quarter wave lengths corresponding to the operating frequency, and is preferably adjusted to operate at the three-quarters wave length point. A suitable choice of the physical length of the anode-grid cavity is determined, among other things, by the type of output electrode means which it is contemplated using. For example, in the system illustrated in Fig. 1 if an appreciable axial adjustment of the output electrode means is contemplated, it has been found that a three-quarters wave length cavity permits adequate space for the adjustment of the output electrode means. The combination of an electric discharge device having transverse disklike terminals and concentric resonators is dis-- closed and claimed in the copending Jensen and Keister application, Serial No, 448,206, filed June 1942 and assigned to the assignee of this invention. Patentable subject matter generic to the Jensen and Keister application and this application is the prior invention of Jensen and Keister.

In the operation of the system shown in Fig. 1, upon establishment of the excitation of the grid-cathode cavity through the associated concentric transmission line there will be established in the anode-grid cavity an amplified electromagnetic excitation, the coupling between the two cavities being accomplished principally by the interelectrode capacitances of the discharge device I. The amount of regenerative action occurring in the system may be controlled or adjusted by the position of the output electrode means comprising disk 29.

As the output electrode means including disk 29 is adjusted axially or longitudinally, the effective impedance of the anode-grid cavity varies; this impedance decreases as the output electrode means is moved towards the electric discharge device. l. Consequently, as viewed from an elementary point of view, it may be considered that as the output electrode means is advanced towards. the discharge device I the load imposed on the anode-grid cavity is increased.

Variation in the position of the output electrode means also controls the amount of energy fed back from the anode-grid cavity to the gridcathode cavity through the coupling between these two cavities comprising principally the anode-cathode interelectrode capacitance of discharge device i. It will then be appreciated that by adjustment of the output electrode means, the

voltage of the anode-grid cavity is consequently controlled, thereby controlling the amount of energy which is fed back to the grid-cathode cavity through the interelectrode capacitance aiforded by the anode and the cathode. Accordingly, by the adjustment of the output electrode means, the amount of regenerative action between the two cavities is readily controllable, making it possible to establish positions wherein regeneration or absence of regeneration is selectively obtainable,

I have found that, within certain operating wavelengths, receiver amplifiers built in accordance with the above described structure and principles are susceptible of performing with a sensitivity better than that of a crystal, thereby I affording a system of high sensitivity as well as substantial power output.

Curves A and B of Fig. 2 represent operating characteristics, particularly gain versus operating wave length, of systems employing the above described features of construction and operation and using electric discharge devices of somewhat different characteristics. The variation of operating wave length is accomplished by con-' trollin the axial position of rod l8 and member 2i for a given setting of the tuning member 3!. Apparatus built in accordance with the above described features offer distinct advantages including improvements in the signal-to-noise ratio over that obtainable by ultra high frequency space resonant systems developed heretofore.

While my invention has been described principally in connection with an ultra high frequency amplifier, it will be appreciated that certain aspects thereof are applicable to space resonant systems generally and it will be obvious to those skilled in the art that changes and modification may be made without departing from my invention, and I, therefore, aim to cover in the appended claims all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes comprising an anode, a grid and a cathode supported by a plurality of transversely extending members interconnected by means of insulators sealed in end relation thereto, said transverse members serving as externally accessible high frequency terminals, a pair of substantially closed cavity resonators connected respectively with the anode-grid and the grid-cathode circuits of said discharge device, the anode-grid resonator comprising an elongated cylinder connected to the grid transverse member and having therein in spaced relation a longitudinal rod connected to said anode, the grid-cathode resonator being defined by an annular member of shorter length and substantially larger diameter than said cylinder, input electrode means coupled to the gridcathode resonator, means for tuning said gridcathcde resonator including means for modifying a bounding surface thereof, means for tuning the anode-grid resonator comprising means movable with respect to a part of said anode-grid resonator for adjusting the effective longitudinal length thereof, and output electrode means connected to said anode-grid resonator.

2. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode supported by three transversely extending accessible members which progressively increase in diameter in the order named and which afford externally accessible high frequency terminals to the electrodes, an anode-grid cavity resonator including a conductive cylinder of elongated configuration connected to the grid transverse member, a grid-cathode cavity resonator including an annular member of larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and said grid, and means for tuning the anode-grid resonator comprising a longitudinally adjustable anode connecting rod within said cylinder and having at one end thereof an electromagnetic wave filter member positionable with said rod.

3. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode supported by three transversely extending externally accessible members which progressively increase in diameter in the order named and which afford externally accessible high frequency terminals to the electrodes, an anode-grid cavity resonator including a conductive cylinder of elongated configuration connected to the grid transverse memher, a grid-cathode cavity resonator including an annular member of larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and said grid, means for tuning the anode-grid resonator comprising a longitudinally adjustable anode connecting rod within said cylinder and having at one end thereof a cup-shaped electromagnetic wave filter member positionable with said rod, and means for tuning said grid-cathode resonator including means for adjusting a bounding surface thereof.

4. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode supported by three transversely extending externally accessible members which progressively increase in diameter in the order named and which afford externally accessible high frequency terminals to the electrodes, an anode-grid cavity resonator including a conductive cylinder of elongated configuration connected to the grid transverse member, a grid-cathode cavity resonator including an annular member of larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and said grid, means for tuning the anode-grid resonator comprising a longitudinally adjustable anode connecting rod within said cylinder and having at one end thereof a cup-shaped electromagnetic wave filter member positionable with said rod, and means for tuning the gridcathode resonator comprising a radially adjustable stub extending within said grid-cathode resonator.

An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode supported by three transversely extending externally accessible members which progressively increase in diameter in the order named and which afford externally accessible high frequency terminals to the electrodes, an anode-grid cavity resonator including a conductive cylinder of elongated configuration connected to the grid transverse member, a grid-cathode cavity resonator including an annular member of larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and said grid, means for tuning the anode-grid resonator comprising a longitudinally adjustable anode connecting rod within said cylinder and having at one end thereof a cup-shaped electromagnetic wave filter member positionable with said rod, and means for tuning the grid-cathode resonator comprising a metallic member extending therein and adjustable with respect to the end of said cylinder connected to the grid transverse member.

6. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode supported by three transversely extending externally accessible members which progressively increase in diameter in the order named and which afford externally accessible high frequency terminals to the electrodes, an anode-grid cavity resonator including a conductive cylinder of elongated configuration connected to the grid transverse member, a grid-cathode cavity resonator including an annular member of larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and said grid, means for tuning the anode-grid resonator comprising a longitudinally adjustable anode connecting rod within said cylinder and having at one end thereof a cup-shaped electromagnetic Wave filter member positionable With said rod, input electrode means coupled with the grid-cathode resonator, and output electrode means extending into the anode-grid resonator.

'7. An ultra high frequency device of the cavity 8 resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode supported by three transversely extending externally accessible members which progressively increase in diameter in the order named and which afford externally accessible high frequency terminals to the electrodes, an anode-grid cavity resonator including a conductive cylinder of elongated configuration connected to the grid transverse member, a grid-cathode cavity resonator including an annular member of larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and said grid, means for tuning the anode grid resonator comprising a longitudinally adjustable anode connecting rod extending through said cylinder and having at one end thereof a cupshaped electromagnetic wave filter member positionable with said rod, input electrode means coupled with the grid-cathode resonator, and output electrode means extending into the anodegrid cavity and positionable longitudinally to control the regenerative action between the two resonators.

8. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes comprising an anode, a grid and a cathode, transverse metallic members connected to said respective electrodes and providing externally accessible high frequency terminals therefor, an anode-grid cavity resonator including a metallic cylinder connected to the grid transverse member, a gridcathode cavity resonator of a longitudinal length corresponding approximately to the distance between anode and cathode transverse members of said discharge device and being of substantially larger diameter than said cylinder, input electrode means coupled with the grid-cathode resonator, a longitudinally adjustable anode connecting rod within said cylinder, means for applying a unidirectional potential to said rod, and means for tuning the anode-grid resonator comprising tuning structure supported by and positionable with said connecting rod.

9..An ultra high frequency amplifier of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes comprising an anode, a grid and a cathode supported by a plurality of transversely extending members interconnected by means of insulators sealed in end-to-end relation, said transverse members serving as externally accessible high frequency terminals, a pair of substantially closed cavity resonators connected respectively with the anode-grid and the gridcathode circuits of said discharge device, the anode-grid resonator comprising an elongated cylinder connected to the grid transverse member and having therein in spaced relation a longitudinal rod connected to said anode, the gridcathode resonator being defined by an annular member of shorter length and substantially larger diameter than said cylinder, input electrode means coupled with the grid-cathode resonator, tuning means for controlling the resonant frequency of said grid-cathode resonator includ ing means for modifying a bounding surface of, and output electrode means connected to said anode-grid resonator.

10. An ultra high frequency amplifier of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes comprising an anode, a grid and a cathode supported by a plurality of transversely extending members interconnected by means of insulators sealed in end-to-end relation, said transverse members serving as externally accessible high frequency terminals, a pair of substantially closed cavity resonators connected respectively with the anode-grid and the grid-cathode circuits of said discharge device, the anode-grid comprising an elongated cylinder connected to the grid transverse member and having therein in spaced relation a longitudinal rod connected to said anode, the grid-cathode being defined by an annular member of shorter length and substantially larger diameter than said cylinder, input electrode means coupled with the grid-cathode resonator, means for tuning the anode-grid resonator comprising means positionable with the longitudinal rod for controlling the effective electrical length of the anode-grid resonator, and output electrode means connected to said anode grid resonator.

11. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode, transverse metallic members connected to said respective electrodes and providing externally accessible high frequenc terminals, an anode-grid cavity resonator including a conductive cylinder connected to the grid transverse member, a gridcathode space resonant cavity defined by an annular member of substantially larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and grid, means for tuning said anode-grid resonator including means for adjusting a bounding surface thereof, input electrode means coupled with said grid-cathode resonator, and means projecting into said grid-cathode resonator for controlling the capacitance thereof to control the natural frequency thereof.

'12. An ultra high frequency device of the cavity resonator type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode, transverse metallic members connected to said respective electrodes and providing externally accessible high frequency terminals, an anode-grid cavity resonator including a conductive cylinder con- 10 nected to the grid transverse member, a gridcathode resonator including an annular member of substantially larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and grid, means for tuning said anode-grid resonator, input electrode means coupled with said gridcathode resonator, and means movable with respect to a part of said grid-cathode resonator for changing the volume thereof and to control the natural frequency thereof.

13. An ultra high frequency system of the space resonant type comprising an electric discharge device including a plurality of enclosed electrodes including an anode, a grid and a cathode, transverse metallic members connected to said respective electrodes and providing externally accessible high frequency terminals, an anode-grid cavity resonator including a conductive cylinder connected to the grid transverse member, a grid-cathode cavity resonator including an annular member of substantially larger diameter and of smaller longitudinal length than said cylinder and electrically connected to said cathode and grid, input electrode means coupled with said grid-cathode resonator, and means for controlling the capacitance of said grid-cathode resonator to control the natural frequency thereof comprising adjustable screw means extending through said annular member and having an end spaced from said conductive cylinder in the vicinity of said grid transverse member.

FRANCIS M. BAILEY.

REFERENCES CITED lfhe following references are of record in the file of this patent:

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